The present invention is especially applicable to mining machines and the like of the type having a primary drive member to which is affixed one or more base members each adapted to receive a bit lug which in turn receives a bit or cutting tool. The drive member, which in turn is driven by appropriate mechanisms, may take a number of forms such as a chain, a rotating wheel, a rotating drum, or a rotating arm and the like. The bits or cutting tools, which may also be those found in machinery other than mining, such as road working and earth moving equipment, may also take various forms such as mining machine cutter bits, road ripping elements, digger teeth and the like.
The bit lug, also known in the trade as a bit block or bit holder, may receive various kinds of bits or cutting elements. To this end the lug is provided with a perforation designed to receive the shank of the particular style of bit for the particular work to be performed. The precise relationship between the bit lug and bit does not constitute a direct part of the instant invention. Various means may be provided for retaining the bit or cutting element within the lug; again these do not constitute a direct part of the instant invention. By the same token the invention is not directly concerned with the particular kind of equipment to which the base member, that which receives the bit lug, is affixed. The invention is primarily concerned with the manner by which the bit lug is secured within a cavity provided for it in the base member. As indicated herein, means are provided to retain the bit lug within the base member and the invention is directly concerned with protecting these latter means.
No search of the prior United States patent art has been made in connection with this invention. It is known, however, that there are many patents which show various relationships between bit lugs and base members. Prior art workers recognized the importance of providing arrangments by means of which the bit lug itself, as distinguished from the bit per se, could be easily and readily removed from the respective base member in which it was mounted. A number of "pin-on", "wedge-on" and other arrangements were developed for accomplishing such result. U.S. Pat. No. Re. 28,310 discloses a popular "pin-on" arrangement for securing a bit lug to a base member. Various "wedge-on" arrangements are shown in U.S. Pat. Nos. 3,342,531; 3,834,764; 4,057,294; 4,275,929 and 4,337,980. (Patents such as U.S. Pat. Nos. 3,397,012 and 3,622,206 disclose various means and arrangements for enabling quick and easy removal of a bit from a bit lug. Other such means and arrangements are shown in U.S. Pat. Nos. 2,965,365 and 3,114,537.)
There is other art which is at least indirectly pertinent. U.S. Pat. Nos. 3,679,265 and 3,888,133, for example, show chains made up of various interdigitated bit-carrying links, connecting links, spacers, connecting pins and retaining means. U.S. Pat. No. 3,888,133 is of interest in that it does disclose an arrangement by which the means to retain a connecting pin within a number of connecting links, bit-carrying links and spacers is prevented from being accidentally dislodged and is protected from wear. Some of the principles of this latter patent are adopted for use in the instant invention. In this connection, U.S. Pat. No. 3,397,012 (FIG. 12) is also of interest.